Equipment for manufacturing of containers from blanks of a cardboard based material is described in e.g. EP0074343. Such equipment normally includes a container body forming unit where a cylindrical container body is formed from a substantially plane blank of a multilayer material comprising at least a supporting cardboard layer and a weldable, plastic layer. In a welding unit, an end closure, a bottom, is applied to the inside of the container body by inducing welding energy and melting the weldable layer. Such a welded joint is well known to be capable of being gas tight. After welding the bottom edge of the container body is normally processed in an edge shaping unit where the edge typically is folded, heated and curled to provide stability and a more appealing appearance. Also the body blank may be welded together as to form the cylindrical container body, but welding of the end closure is usually a more complex process step.
Often both the container body and the end closure form multilayer structures where a weldable plastic film is applied to the inside of the cardboard based lid and container. In particular for food products, the layer structure usually includes a layer of aluminium arranged between the cardboard and the plastic layer. Typically, a high frequency current energy is induced in the aluminium layer, which foil thereby gets heated and in turn melts the plastic film. Automated equipment of this type further comprises transporting means configured to transport a flow of containers from the container body forming unit to the welding unit and further downstream in the equipment.
Equipment for filling the containers and for sealing and closing the filled containers can be arranged in connection to the container manufacturing equipment.
An important issue in this context is the production rate, i.e. the number of containers per, say, minute that can be manufactured. To be commercially successful, the apparatus used for manufacturing the containers must allow for a high production rate.
A problem when trying to increase the production rate of conventional equipment is that the weldable layer does not get sufficient time to heat up, cool and harden before the containers are removed and transported away from the welding unit. This often results in a damaged and leaking joint. Various heating and cooling devices, as well as different weldable material, have been proposed for carrying out the step of fastening the end closures more quickly but their performance has not been satisfactory.
Thus, there is still a need for equipment of the above mentioned type that allow for a higher production rate.